A measuring device developed as a radar device is described in German Published Patent Application No. 100 50 278 or from the dissertation by M.-M. Meinecke “Regarding Optimized Transmission Signal Design for Automobile Radars”, Technical University Hamburg-Harburg, 2001. German Published Patent Application No. 100 50 278 describes the determination of a distance and of a relative speed of at least one distant object from an observation point with the aid of electromagnetic signals emitted from the observation point in the form of alternately emitted signal portions of a first frequency and of a second frequency, which following a reflection by the object are received and evaluated, the signal portions of the two frequencies being emitted during a measuring interval such that they are shifted in each case by one constant frequency increment.
The use of a radar device in the automotive sector is also described in the dissertation “Radar Systems for the Automatic Distance Control in Automobiles” by R. Mende, Technical University Carolo-Wilhelmina, Braunschweig, 1999, as well as German Published Patent Application No. 199 22 411, German Published Patent Application No. 42 44 608 and German Published Patent Application No. 100 25 844.
German Published Patent Application No. 199 22 411 describes a CW radar method (continues wave radar method) for measuring distances and relative speeds between a vehicle and one or several obstacles, in which a transmission signal is made up of at least four consecutive blocks having in each case different gradients. In a distance-relative speed diagram, first the intersections of all straight lines from two blocks of all discovered frequency positions are calculated. For validating these intersections, they are checked as to whether in the Fourier spectrum of a third block there exists a peak at a frequency position, whose associated straight line in the distance-relative speed diagram intersects a surrounding region of the intersection. The intersections validated in this manner are subjected to a second condition, whether in the Fourier spectrum of a fourth block there exists a peak at a frequency position, whose associated straight line in the distance-relative speed diagram intersects a surrounding region of the intersection. The intersections are regarded as valid if they satisfy both conditions.
German Published Patent Application No. 42 44 608 describes a radar method for measuring distances and relative speeds between a vehicle and obstacles in front of it, comprising an emission of continuous transmission signals, simultaneous reception of signals reflected by the obstacles during the emission of the continuous transmission signals, mixing of the reflected signals with the continuous transmission signals for obtaining inphase and quadrature signals and processing of these signals into output signals for the distances and relative speeds of the obstacles, the continuous transmission signals being broken down into constant frequency increments of constant time duration without time interval with respect to each other and at each constant frequency increment of the reflected received signal a complex sampling value being recorded and mixed with the transmission signal of the same constant frequency increment.
German Published Patent Application No. 100 25 844 describes an incrementally linear frequency-modulated transmission signal, at least two incrementally linear frequency-modulated ramps being mutually interwoven. Characteristic in this regard is the fact that these two or more ramps have a constant frequency shift with respect to one another. By frequency measurement and phase difference measurement it is possible to calculate unambiguously the distance of the object and the speed of the object from the received signals.
In addition it is describe in German Published Patent Application No. 43 31 440 to form for the radar device I/Q signal pairs for the signal evaluation, a phase shifter being connected between a radar antenna and a radar front end, an evaluation circuit having two signal channels on the input side, the radar front end being connectable via a channel switch to one of the two signal channels, the phase shifter and the channel switch being clocked synchronously and the phase shifter switching the phase between 0° and 45° with each clock cycle.
A Doppler radar device for a vehicle for indicating a distance between the vehicle and an obstacle is described in German Published Patent Application No. 689 13 423.